BMS248 Lecture 12 - Drosophila Olfactory Learning Flashcards
In classical conditioning when should the conditioned stimulus occur in regards to the unconditioned stimulus?
The conditioned stimulus shoiuld coincide with or precede the unconditioned stimulus - I.e. the conditioned stimulus predicts the unconditioned stimulus
What is the drosophila olfactory pathway beginning at the odour?
- Odour
- Olfactory receptor neurons
- Projection neurons (2nd order)
- Kenyon cells (3rd order) - CS
- Dopaminergic neurons - US
- Mushroom body output neurons
3rd order neurons (Kenyon cells) sample what to respond to respond selectively to odours?
2nd order - projection neurons
What do drosophila Kenyon cells receive input from? What do they require to fire?
Multiple projection neurons
Require multiple simultaneous inputs to fire from projection neurons - sparse coding
What type of memory are Kenyon cells the site of?
Associative memory storage - DA + KC = plasticity at the synapse
What does the GAL4/UAS system allow you to artificially express in specific cells?
Arbitrary transgenes - GAL4 binds to UAS which recruits transcription factors to initiate transcription downstream of UAS
What is the split-GAL4 system? Advantages?
Has an extra activation domain which is required to drive gene expression - increased specificity
What cell type is the mushroom body made up of?
Kenyon cells
Kenyon cell axons are subdivided into compartments by
innervation by what two types of neurons?
- Mushroom body output neurons (MBONs)
- Dopaminergic neurons (DANs)
- innervation patterns match
How are Kenyon cell axons subdivided?
One-to-one matching of dopaminergic neurons (DANs) and mushroom body output neurons (MBONs), tiling axons of Kenyon cells
Some MBONs lead to what BEHAVIOUR when activated optogenetically?
Approach/avoidance behaviour
Some DANs, when activated optogenetically can entrain what MEMORY?
Aversive or appetitive memory
Reward DANs encode the same areas as what kind of MBONs?
Reward DAN - Avoidance MBON
Punishment DAN - Approach MBON
(Opposite)
During learning, dopamine signalling has what effect on synapses between KCs and MBONs?
During learning, DANs locally depress synapses between KCs and MBONs - leading to the ‘wrong’ action.
I.e. avoidance behaviour arises from a weakening of synapses on ‘approach’ MBONs
What is the difference between forward and backward pairing?
Forward pairing - CS before US - e.g. odour then reward
Backward pairing - US before CS
In FORWARD pairing (i.e. learning) what happens to the response at KC-MBON synapses?
Depressed - decrease in respond after pairing - due to cAMP
In BACKWARD pairing what happens to the response at KC-MBON synapses?
Potentiate - increase in response after pairing - due to Ca2+
What are the two types of Kenyon cell dopamine receptors and their signalling pathways?
- DopR1 - Gs - ^ cAMP - aquisition
- DopR2 - Gq - ^ ER Ca2+ - forgetting
What pairing is DopR1 associated with?
Acquisition of memory - forward pairing - depression
What pairing is DopR2 associated with?
Forgetting memory - backward pairing - potentiation
What can be used to measure the activity of DopR1?
EPAC - sensor for cAMP
What can be used to measure the activity of DopR2?
ER-GCaMP - measures ER calcium
What is released during forward conditioning compared to backward?
cAMP released during both forward and backward conditioning.
Whereas Ca2+ release only for backward.
ER Ca2+ release is only allowed if IP3 –> Ca2+ - how?
The channel is a coincidence detector - calcium locks channel into a closed position if Ca –> IP3 - order of events
How is the insect mushroom body similar to cerebellar like structures?
- Projection neurons = Mossy fibres
- Kenyon cells = Granule cells
- DANs = Climbing fibres
- MBONs = Purkinje cells
Cerebellum mediates what? How is this similar to the mushroom body?
Mediates motor learning - partly about correcting ‘wrong’ movements
It is a common structure for ‘error correction’
